What happened
On March 13, 1996, a Piper PA-31T1 Cheyenne, registration PT-WHN, was performing a flight from Cascavel to Foz do Iguaçu with one pilot and three passengers. As the aircraft approached the Foz do Iguaçu aerodrome, the pilot was instructed by Air Traffic Control to contact the Tower. While approximately 2 NM from the runway threshold, the pilot initiated a right turn to intercept the downwind leg for runway 32.
During this maneuver, the Tower Controller queried the pilot's intentions. The pilot responded by declaring an emergency, but did not specify the nature of the problem. Witnesses in the control tower observed the aircraft enter an abnormal attitude, eventually turning inverted. The aircraft subsequently struck the ground in a nose-down attitude, resulting in a concentrated impact and an immediate explosion. All four fatalities occurred at the scene, and the aircraft was a total loss.
The investigation
The CENIPA investigation examined the aircraft's mechanical condition, the pilot's training, and the environmental factors. Technical analysis of the turboprop engines by the IFI/CTA concluded that both powerplants were fully operational and had been operating at speeds slightly above idle at the time of the accident, ruling out engine failure as a cause. The aircraft's weight and balance were within limits, and maintenance records were up to date.
Investigators also reviewed the pilot's experience and training. While the pilot was highly experienced in total flight hours, he had only 80 hours of experience in the PA-31T1, much of which was gained during transit rather than local training. The investigation also noted that the aircraft was being operated by a single pilot, despite the type typically requiring a two-person crew.
Findings
- The pilot's lack of local training and limited experience in the PA-31T1 contributed to the inability to manage the aircraft's characteristics during a critical phase of flight.
- The Piper Cheyenne is known for having reduced lateral stability, where a pilot may inadvertently exceed the desired bank angle if commands are not actively countered.
- The pilot was likely experiencing high workload due to the single-pilot operation, the need to manage communications during an emergency, and the approach of an active Cumulonimbus (CB) formation which brought turbulence and rain to the area.
- Deficient supervision by the operator regarding crew training and operational limitations was a contributing factor.
- The pilot's inability to apply corrective commands prevented the recovery from the abnormal attitude.